Polysaccharides FDSC400

Sources of Polysaccharide Microbial fermentation Higher plants –seeds, –tree extrudates, –marine plants, Chemical modification of other polymers No calorific value; fiber

Solubility Strong interaction with water = solubility Strong, extended interaction with polymer = insolubility Local, limited interaction with polymer = gelation

Gelation Cross links – covalent, ion pairing, co- crystallization

Viscosity The radius of gyration is the sphere swept out by the polymer

Xanthan gum Source: Product of bacteria Xanthomonas campestris Structure: cellulose-like backbone (  -1,4-poly- glucose) with trisaccharide branches (stubs) on alternate monomers on the backbone carrying carboxylic acid residue Functional Properties: Water soluble, viscous, non-gelling. Viscosity is only slightly temperature dependant

Low pH Linear molecule Random coil Xanthan: Structure-function

Pectin Source: Cell walls of higher plants (citrus rind) Structure: Largely a linear polymer of polygalacturonic acid with varying degrees of methyl esterification. (Also some branches – HAIRY REGIONS) –>50% esterified is a high methoxy (HM) pectin –<50% esterified is a low methoxy (LM) pectin Functional Properties: High methoxy pectin will gel in the presence of acid and high sugar concentrations. Low methoxy pectin will gel in the presence of calcium.

%DE of Pectin Gel with Ca 2+ Gel with acids and low water High and Low Methoxy Pectin HMP LMP

Algin Source: Seaweed extract Structure: linear polysaccharide containing two types of residue (i.e., a co-polymer):  -D- mannopyranosyluronic acid and (M)  -L- gulopyrasonic acid (G) Functional Properties: Viscous in aqueous solution, gels in the presence of Ca 2+ (or low pH). Gels are temp stable PGA (propylene glycol alginate)

Ca 2+ G-block M-block “Egg-box” Structure

Cellulose Gums  1-4  1-4

CarboxymethylcelluloseMethylcellulose (may gel at high T)

Carboxymethyl cellulose -CH 2 COO - High viscosity, non-gelling

Carageenan Source: Seaweed gum Structure: Linear D-galactopyranosyl chain with alternating 1,3 and 1,4 links. Some residues have one or two sulfate ester residues. Three broad types of repeating structure ( , , and carageenan) Functional Properties: pH independent thickening. Double helix formation in  or  carageenan can lead to gelation. –  -carageenan in dairy foods

Gum Arabic Extrudate gum of the acacia tree Expensive – hard to source Low viscosity, non-gelling Complexed with a glycoprotein -surface active